A hybrid vehicle using a motor for a vehicle driving system, electric vehicle or battery forklift is provided with a battery for driving the traveling motor, in which AC power is supplied from the battery to the motor through an inverter.
Industrial vehicles such as battery forklifts employ lead batteries as power sources and taking into consideration the energy which these industrial vehicles consume during traveling or work operation, the battery capacity must be large enough.
Even when a vehicle has a large capacity battery, if the battery is a lead battery, it may happen that most regenerative energy in regenerative braking is lost and cannot be recovered since the lead battery is not suitable for rapid charging.
Therefore, in recent years, an attempt to improve efficiency has been made by combining a battery and a capacitor to constitute a power supply system and storing the energy from a load in the capacitor and making it possible to supply the stored energy to the load instantaneously.
For example, Patent Literature 1 describes a power supply system as a combination of a battery and a capacitor in which a current-voltage converter is placed between the charge-discharge capacitor and battery and in the drive control mode of a motor as a load, the capacitor is connected to a discharge path and in the regenerative braking mode of the motor, the capacitor is connected to a charge path so as to decrease the capacity of power supply such as the battery and supply the required maximum energy to the load.